Downhole tool piston assembly

ABSTRACT

A piston assembly may comprise a housing with a wall, and at least one chamber formed in the wall. A piston may be disposed within the chamber and at least one passageway may pass through the piston. At least one pin may be disposed within the passageway and attached to the chamber, and the piston may be free to translate relative to the pin.

Notice: More than one reissue application has been filed for the reissueof U.S. Pat. No. 9,085,941. The reissue applications are applicationSer. Nos. 15/164,663 and 16/150,875 (the present application). Thepresent application is a divisional reissue of U.S. Pat. No. 9,085,941and application Ser. No. 15/164,663 is a reissue of U.S. Pat. No.9,085,941.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional reissue application of U.S. patentapplication Ser. No. 15/164,663, filed May 25, 2016, which is a reissueof U.S. Pat. No. 9,085,941, issued on Jul. 21, 2015. This application isalso a reissue application of U.S. Pat. No. 9,085,941, issued on Jul.21, 2015.

BACKGROUND OF THE INVENTION

The present invention relates to the fields of downhole oil, gas, and/orgeothermal exploration and more particularly to piston assemblies foractuating downhole tools. There exists in the art a variety of downholetools comprising piston assemblies configured to actuate downhole toolsto protrude and retract. One such downhole tool may be a directionalsteering mechanism. In directional drilling operations, a piston mayextend a pad that contacts a formation and causes the drill string tomove in a direction. Other such tools include expandable toolsconfigured to enlarge the diameter of a wellbore and/or stabilize adrill string. The expandable tools may contain arms or blades whichextend from the sides of the drill string and contact the formation.Examples from the prior art of such piston assemblies used in downholetools are given below.

U.S. Patent Publication No. 2010/0071962 to Beuershausen, which isherein incorporated by reference for all that it contains, discloses adrill bit that includes at least one blade profile having a side sectionand an adjustable pad on the side section that is configured to extendfrom the side section to cause the drill bit to alter a drillingdirection when the drill bit is used to drill a wellbore.

U.S. Patent Publication No. 2010/0139980 to Neves et al., which isherein incorporated by reference for all that it contains, discloses aball piston steering device and methods for use of ball piston devices.One aspect of the invention includes: a sleeve in fluid communicationwith a fluid source and a ball received within the sleeve. The ball ismovable within the sleeve from a recessed position and an extendedposition.

U.S. Patent Publication No. 2006/0157283 to Hart, which is hereinincorporated by reference for all that it contains, discloses a biasunit comprising at least one bias pad moveable by a piston betweenretracted and extended positions wherein the piston is of non-circulareffective cross-sectional shape.

U.S. Patent Publication No. 2004/0206549 to Dewey et al., which isherein incorporated by reference for all that it contains, discloses adownhole tool that functions as an underreamer or as a stabilizer in anunderrreamed borehole. The tool includes one or more moveable armsdisposed within a body having a flowbore therethrough in fluidcommunication with the wellbore annulus. The tool alternates betweencollapsed and expanded positions in response to differential fluidpressure between the flowbore and the wellbore annulus. In oneembodiment, the tool moves automatically in response to differentialpressure. In a second embodiment, the tool must be selectively actuatedbefore it is moveable. The tool may include borehole engaging pads thatcomprise cutting structure or wear structures or both, depending uponthe function of the tool.

Despite the advancements as shown in the prior art, it is believed thatthere is still a need to develop improved piston assemblies used indownhole drill strings.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the present invention, a piston assembly may comprise ahousing with a wall, and at least one chamber formed in the wall. Apiston may be disposed within the chamber and at least one passagewaymay pass through the piston. At least one pin may be disposed within thepassageway and be attached to the chamber, and the piston may be free totranslate relative to the pin.

The housing may be selected from a group consisting of drill bits,calipers, reamers, shock absorbers, jars, clamps, tractors, stabilizers,fishing tools, and combinations thereof. When the housing consists of adrill bit, the wall and the chamber may be disposed on a gauge surfaceof the drill bit. The housing may comprise a tube and the wall may bedisposed within or on a surface of the tube. The chamber may be in fluidcommunication with a fluid source.

The chamber may comprise a cross section selected from the groupconsisting of a circle, oval, polygon, star, rectangle with circularends, and annulus. The chamber may be lined with a sleeve and thechamber and the sleeve may comprise openings to allow passage of the atleast one pin. The chamber openings may also allow fluid communicationwith the chamber. A seal may be disposed between the chamber and thepiston, the piston and the sleeve, or the chamber and the sleeve.

The piston may comprise a cross sectional shape similar to the chamber.The piston may comprise a working surface adjacent the wall, a basesurface opposite the working surface, and an intermediate surfacejoining the working surface and the base surface. The working surfacemay comprise wear resistant elements disposed thereon. The base surfacemay be nonplanar and comprise a topography selected from the groupconsisting of grooves, dimples, flutes, fins, troughs, and protrusions.The base surface may also comprise an opening to the passageway. Thepassageway may intersect at least one of the intermediate surface andthe base surface.

The pin may comprise a cross section selected from the group consistingof a circle, oval, polygon, star, rectangle with circular ends, andannulus. The pin may also comprise a sleeve surrounding at least aportion of the pin, and an aperture there through. The passageway maycomprise a cross-sectional area greater than a cross-sectional area ofthe pin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an orthogonal view of an embodiment of a drilling operation.

FIG. 2 is an orthogonal view of an embodiment of a drill bit comprisinga plurality of pistons disposed on its outer wall.

FIG. 3 is a cross-sectional view of an embodiment of a drill bit with aplurality of pistons in an extended position.

FIG. 4 is a cross-sectional view of an embodiment of a piston disposedwithin a drill bit.

FIG. 5a is a perspective view of an embodiment of a pin with anaperture.

FIG. 5b is a cross-sectional view of an embodiment of a pin.

FIG. 5c is an orthogonal view of an embodiment of a pin with a groove.

FIG. 6a is an orthogonal view of an embodiment of a piston with apassageway disposed in the center of the piston.

FIG. 6b is a perspective view of another embodiment of a piston.

FIG. 7a is an orthogonal view of an embodiment of a piston with apointed working surface.

FIG. 7b is an orthogonal view of an embodiment of a piston with aserrated working surface

FIG. 7c is an orthogonal view of an embodiment of a piston comprising atleast one cutting element.

FIG. 7d is an orthogonal view of an embodiment of a piston retained in atool by a shoulder.

FIG. 8a is an orthogonal view of an embodiment of a chamber comprising around shape.

FIG. 8b is an orthogonal view of an embodiment of a chamber comprising aquadrilateral shape.

FIG. 8c is an orthogonal view of an embodiment of a chamber comprising atriangular shape.

FIG. 8d is an orthogonal view of an embodiment of a chamber comprising apolygonal shape.

FIG. 9a is a cross-sectional view of an embodiment of piston with a pinintruding therein.

FIG. 9b is an orthogonal view of an embodiment of a piston comprising anopening for the intruding pin.

FIG. 9c is a cross-sectional view of an embodiment of a piston with twopins disposed on opposite edges of the piston.

FIG. 9d is an orthogonal view of an embodiment of a piston with tworecesses disposed on opposite edges of the piston.

FIG. 9e is a cross-sectional view of an embodiment of a piston with twopins disposed therein and perpendicular with respect to each other.

FIG. 9f is an orthogonal view of an embodiment of a piston with twoopenings for the perpendicular pins.

FIG. 10 is a cross-sectional view of an embodiment of a drill bitassembly with a piston disposed within and configured to push against aninner bit.

FIG. 11 is an orthogonal view of an embodiment of a plurality of pistonsdisposed on a drill string forming a reamer tool.

FIG. 12 is an orthogonal view of an embodiment of a plurality of pistonsdisposed on a drill string forming a clamping tool.

FIG. 13 is an orthogonal view of an embodiment of a plurality of pistonsdisposed on a drill string, forming a crawler tool.

FIG. 14 is an orthogonal view of an embodiment of a plurality of pistonsdisposed on a drill string and the pistons comprise at least one sensor.

FIG. 15 is a cross-sectional view of an embodiment of piston disposedwithin a cutting face of a drill bit.

DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENT

Referring now to the figures, FIG. 1 discloses an embodiment of adrilling operation comprising a downhole tool string 100 suspended by aderrick 101 in a wellbore 102. A steering assembly 103 may be located atthe bottom of the wellbore 102 and may comprise a drill bit 104. As thedrill bit 104 rotates downhole, the downhole tool string 100 may advancefarther into a subterranean formation 105. The steering assembly 103 maybe adapted to steer the drill string 100 in a desired trajectory. Thedrill string 100 may also comprise other tools 107. The tools 107 may beexpandable tools used for enlarging the wellbore 102 or stabilizing thedrill string 100 in the formation 105. The downhole tool string 100 maycomprise electronic equipment able to send signals through a datacommunication system to a computer or data logging system 106 located atthe surface.

FIG. 2 discloses an orthogonal view of an embodiment of the drill bit104 connected to the drill string 100. The drill bit 104 may comprise acutting face 201 and a gauge surface 202. The drill bit 104 may comprisea plurality of blades 215 converging at a center of the cutting face 201and diverging at the gauge surface 202. The blades 215 may be equippedwith cutting elements 220 configured to degrade the formation 105. Fluidfrom drill bit nozzles 225 may remove formation fragments from thebottom of the wellbore and carry them up an annulus 203 of the wellbore.

The present embodiment discloses the drill bit 104 configured to be ahousing for a piston assembly 204. At least one chamber (hidden fromview) may be formed in a wall 205 of the housing on the gauge surface202. A piston 206 may be disposed within each chamber and may beconfigured to translate relative to a pin (hidden front view). The pinmay be inserted into the piston 206 to retain the piston 206 in thepiston assembly 204. The pin may be inserted through at least one entrypassageway 207 and attached to the chamber.

The piston assembly 204 may be part of a steering mechanism configuredto steer the drill string 100. The piston assembly 204 may steer thedrill string 100 by extending and retracting the pistons 206 which maypush against the formation 105 forcing the drill string 100 to move in adesired direction. At least one chamber may be disposed relative to adesired turning radius of the drill bit 104. It is believed that thecloser the pistons 206 are disposed to the cutting face 201, the greatera build rate can be for the steering mechanism. A 2.5 inch difference inplacing the pistons 206 relative to the cutting face 201 may affect thesteering capability by approximately 3 degrees per 100 feet. Thesteering mechanism of the present invention may dispose the pistonscloser to the cutting face than the steering mechanisms in the prior artdue to the present invention comprising substantially less workingparts. Geometry constraints associated with the amount of working partsis a major limitation in placement of the steering mechanisms. Thepresent invention also comprises smaller components that allow forlarger junk slot volume leading to less restricted mud flow.

FIG. 3 discloses an embodiment of the drill bit 104 comprising at leastone piston assembly 204, each piston assembly 204 comprising a chamber301 and a piston 206 disposed therein. Each chamber 301 may comprise acylinder or other cavity and may be configured to open to a wall 205.The piston 206 may comprise a working surface 302 adjacent to the wall205 and configured to come into contact with the formation. The workingsurface 302 may be convex and configured to match a curvature of thewall 205.

It is believed that a plurality of chambers and pistons disposed in adrill bit may be advantageous in that it provides redundancy. If onepiston becomes jammed or dysfunctional, then another piston may not beaffected and the piston assembly may still perform effectively. Aplurality of pistons may also be configured to actuate independentlyand/or in combination with each other. By acting independently and/or incombination with each other, the pistons may extend and retract atspecified time periods that may maximize the effectiveness of the pistonassemblies. In some embodiments, each piston in the plurality may beconfigured to actuate individually but at determined time intervalswhich may allow the pistons to work off of each other. In someembodiments, the pistons may act in uniform which may increase the pushforce on the formation.

The piston 206 may also comprise a base surface 303 disposed oppositethe working surface 302 and an intermediate surface 308 joining theworking surface 302 and the base surface 303. In some embodiments aretaining passageway 311 may intersect at least one of the intermediatesurface and base surface 303. The base surface 303 may be nonplanar andcomprise a topography selected from a group consisting of grooves,dimples, flutes, fins, troughs, and protrusions which may be in fluidcommunication with a fluid source such as a bore 305 via fluid channels304. The fluid may be drilling mud that is sent through the bore 305 ofthe drill string during normal operation. A valve (not shown) mayredirect a portion of the drilling mud to the fluid channels 304 thuscausing the piston 206 to actuate. In some embodiments, the fluid may beair, gas, foam, oil, water, or a combination thereof.

A pin 306 may retain the piston 206 within the chamber 301. The pin 306may be inserted into the retaining passageway 311 within the piston 206.The pin 306 may allow the piston 206 to translate in a direction normalto a rotational axis 310 of the drill bit 104 but may prevent the piston206 from rotating within the chamber 301. By preventing the piston 206from rotating, the degrees of freedom for the piston 206 are decreasedto only linear movement. The pin 306 may be comprised of tungstencarbide or other hard material that can withstand the rotational loadsthat may act upon the piston 206 during normal operations.

Fluid may push the piston 206 into an extended position and the pin 306may be configured to keep the piston 206 within the chamber 301 byallowing the piston 206 to translate a specified distance. The retainingpassageway 311 may comprise an edge or other stopping device that comesinto contact with the pin 306 and inhibits further translationalmovement of the piston 206. The pin 306 may be adjusted to allow thepiston 206 to translate within a range of 0.010 inch to 0.500 inch. Thepresent embodiment discloses a magnified view of the piston 206extending a distance 307 away from the wall 205.

FIG. 4 discloses another embodiment of a piston 406 disposed in a drillbit 404. This embodiment shows a pin 416 disposed within a retainingpassageway 411 in the piston 406 and attached to a chamber 401. Theretaining passageway 411 may traverse the piston 406 such that the pin416 passes through the piston 406. The piston 406 and chamber 401 maycomprise openings that allow passage of the pin 406. The pin 406 may beinserted into the retaining passageway 411 through an entry passageway417 and a plug 402 may be inserted behind the pin 416 to prevent the pin416 from moving during normal operation.

The chamber 401 may be lined with a sleeve 403 which may also compriseopenings to allow passage of the pin 416. The sleeve 403 may comprise afinish that allows the piston 406 to translate without having toovercome a substantial amount of friction. The sleeve 403 may alsoincrease the life of the piston assembly. During normal operation, thepiston 406 may translate back and forth causing the sleeve 403 to weardown over time. After the sleeve has worn down a specified amount, thesleeve 403 can be replaced. In other embodiments, the walls of thechamber 401 may be in direct contact with the piston 406. However, whenthe walls of the chamber 401 are worn down, the whole piston assemblymay not be functional.

The piston 406 and sleeve 403 may collectively comprise a tighttolerance, around 0.001 inch diametrical difference between the two,that small particles may be prevented from jamming the system. Thepiston 406 and the sleeve 403 may be composed of the same materialallowing them to maintain the tight tolerance under large temperaturechanges.

During normal operations when the piston 406 is extending andretracting, fluid may become trapped within the piston 406. The pin 416may comprise at least one aperture 420 that is configured to allowpassage for the trapped fluid. Trapped fluid may be exhausted by anopening, to the passageway 407 disposed in a base surface 413 of thepiston 406. It is believed to be important to exhaust fluid from insidethe piston 406 as trapped fluid may not allow the piston assembly tofunction properly.

The current embodiment also discloses a seal 408 disposed around thechamber 401. The seal 408 may be disposed between the chamber 401 andthe sleeve 403. In other embodiments a seal may be disposed between thechamber and the piston, or the piston and the sleeve. When operating inhigh pressure environments, fluid may enter or exit the piston assemblybetween the sleeve 403 and chamber 401. The seal 408 may be configuredto prevent fluid from passing through the piston assembly. In someembodiments a seal may not be necessary if the parts of the pistonassembly have a tight tolerance; in other embodiments more than one sealmay be needed.

FIGS. 5a and 5b disclose different views of an embodiment of a pin 506.FIG. 5a discloses a perspective view of the pin 506 comprising anaperture 520. The aperture 520 may be configured to allow trapped fluidto exhaust from the piston assembly.

FIG. 5b discloses a cross-sectional view the pin 506. The pin 506 mayhave a non-circular or partially circular cross section and may compriseflats 501 along its length. As shown in the present embodiment, a top502 and bottom 503 may comprise a partially circular cross section andbe configured to secure the pin 506 within a piston. The flats 501 maybe disposed between the top 502 and bottom 503, may comprise anon-circular cross section, and may be parallel to each other. The flats501 may be configured to allow the piston to translate a specifieddistance. In some embodiments, the pin may comprise a cross sectionselected from the group consisting of a circle, oval, polygon, star,rectangle with circular ends, and annulus.

FIG. 5c discloses an embodiment of a pin 510 comprising a groove 511.The groove 511 may form a smaller cross section than the rest of the pin510 and may be configured to allow passage of trapped fluid from thepiston assembly similar to the aperture as described in FIG. 5a. In thisembodiment the pin 510 also comprises a sleeve 515 surrounding at leasta portion of the pin 510.

FIGS. 6a and 6b disclose different views of an embodiment of a piston606. FIG. 6a discloses the piston 606 comprising a retaining passageway611. The retaining passageway 611 may comprise a substantially similarshape to a pin and a cross-sectional area greater than a cross-sectionalarea of the pin. As the piston 606 translates, the pin may limit thetranslational movement of the piston 606 as the pin comes into contactwith a top edge 602 or a bottom edge 603 of the retaining passageway611.

FIG. 6b discloses a perspective view of an embodiment of the piston 606.The piston 606 may comprise an opening 607 to the retaining passageway611 and topography on a base surface 613. Fluid channels 604 on the basesurface 613 may allow fluid to flow underneath the piston 606 so thatthe fluid can push the piston 606 into an extended position.

FIGS. 7a, 7b, 7c, and 7d each disclose alternate embodiments of pistons.FIG. 7a discloses an embodiment of a piston 703 comprising a pointedworking surface 704. FIG. 7b discloses an embodiment of a piston 705comprising a serrated working surface 706. The embodiments disclosed inFIG. 7a and FIG. 7b may be effective when it is desired that the pistongrips a formation. An example of when it may be desirable for the pistonto grip the formation is when the piston assembly is mounted on adownhole tractor tool.

FIG. 7c discloses an embodiment of a piston 707 comprising at least onecutting element 708 disposed on a working surface 709. The cuttingelement 708 may contact and degrade a formation. An example of when itmay be desirable for the cutting element 708 to be disposed on theworking surface 709 is when the piston assembly is mounted on a downholereamer tool. Cutting elements may be selected from a group consisting ofsteel, stainless steel, hardened steel, nickel-based alloys, cementedmetal carbide, ceramic, diamond, polycrystalline diamond, diamond-likecarbon, or combinations thereof.

FIG. 7d discloses an embodiment of a piston 710 disposed within achamber 711. The piston 710 may be retained within the chamber 711 by ashoulder 712.

FIGS. 8a, 8b, 8c, and 8d each disclose different embodiments of achamber. A chamber may comprise a cross section selected from the groupconsisting of a circle, oval, polygon, star, rectangle with circularends, and annulus. A piston may be disposed within each chamber and maycomprise a shape similar to that of the chamber.

FIG. 8a discloses an embodiment of a chamber 801 formed in a wall 802.The chamber 801 comprises a round shape. The round shape may be circularor oval. The round shape may be advantageous in that it may allow asimilarly shaped piston to not have sharp points that may be susceptibleof breaking during normal drilling operations. The round shape may alsoprovide the maximum contact area for a given perimeter which may allowthe piston to contact a formation with the maximum amount of force, andthe forces may be distributed to the formation across the greatest area.

FIG. 8b discloses an embodiment of a chamber 803 comprising aquadrilateral shape formed in a wall 804. The quadrilateral shape maycomprise any shape with four sides including a square and a rectangle.The quadrilateral shape may provide a reasonable amount of surface areafor a piston disposed within the chamber 803 to contact a formation.

FIG. 8c discloses an embodiment of a chamber 805 comprising a triangularshape. The chamber 805 may be formed within a wall 806 and a piston maybe disposed therein. The triangular shape may consist of being acute,obese, equilateral, equiangular, isosceles, or combinations thereof.FIG. 8d discloses an embodiment of a chamber 807 formed in a wall 808.The chamber 807 may comprise a polygonal shape; in the currentembodiment the chamber 807 comprises an octagonal shape. A polygonalshape may be advantageous in that the chamber 807 may comprise anynumber of sides allowing the chamber 807 and piston to be formatted tohave the most effective shape for a given application.

FIGS. 9a, 9b, 9c, 9d, 9e, and 9f disclose different embodiments of apiston comprising at least one opening configured to allow passage of atleast one pin. The functions of the at least one pin are to keep thepiston inside the piston assembly and to disallow the piston fromrotationally moving.

FIGS. 9a and 9b disclose different views of an embodiment comprising apin 902 intruding but not passing through a piston 901. FIG. 9a shows across-sectional view of the piston 901 disposed within a wall 920 andwith a pin 902 partially disposed within the piston 901. In someembodiments, a plurality of pins may each be disposed partially within apiston at different angles around the piston. FIG. 9b shows anorthogonal view of the piston 901 comprising a retaining passageway 903.The retaining passageway 903 may allow passage of the pin 902 to bepartially disposed within the piston 901.

FIGS. 9c and 9d disclose different views of an embodiment comprising twopins 904 and 905 disposed on opposite edges of a piston 906. FIG. 9cshows a cross-sectional view of the piston 906 disposed within a wall921. Each pin 904 and 905 may comprise an inner side 907 and 908respectively, that may pass through the piston 906 while the rest ofeach pin 904 and 905 is connected to the wall 921. FIG. 9d shows anorthogonal view of the piston 906 comprising two retaining passageways909 and 910. The retaining passageways 909 and 910 may be disposed onopposite edges of the piston 906 and may be configured to allow passageto the pins 904 and 905 respectively.

FIGS. 9e and 9f disclose different views of an embodiment comprising twopins 911 and 912 passing through a piston 913 disposed within a wall922. The pins 911 and 912 may each pass through the center of the piston913 and may be disposed perpendicular with respect to each other. It isbelieved that the two pins 911 and 912 may effectively keep the piston913 from rotating during normal drilling operations. FIG. 9f shows anorthogonal view of the piston 913 comprising two retaining passageways914 and 915. The retaining passageways 914 and 915 may be configured toallow passage to the pins 911 and 912 respectively. The retainingpassageways 914 and 915 may need to be disposed one higher than theother in order for both pins to pass through the piston 913.

FIG. 10 discloses a cross-sectional view of an embodiment of a drill bitassembly 1001 comprising an outer bit 1002 and an inner bit 1003. Theinner bit 1003 may protrude from the outer bit 1002 such that the innerbit 1003 may be the first to come into contact with a formation. Theinner bit 1003 may be advantageous in that it may weaken the formationbefore the outer bit 1002 begins to degrade the formation. The inner bit1003 may also be configured to rotationally move and thus steer thedrill string.

In the present embodiment, a housing comprises a tube and at least onechamber 1004 may be formed in an inside wall 1006 within the tube. Thechamber 1004 may open to the inside wall 1006 thus allowing a piston1007 disposed within the chamber 1004 to come into contact with a body1008 of the inner bit 1003. As the piston 1007 extends and retracts, thepiston 1007 may push the body 1008 of the inner bit 1003 thusrotationally moving the inner bit 1003 and steering the drill string.

FIGS. 11, 12, 13, and 14 each disclose different embodiments of aplurality of pistons disposed in different housings wherein the housingscomprise a tube or drill string, and the wall may be disposed on asurface of the tube. The housings may be selected from a groupconsisting of drill bits, calipers, reamers, shock absorbers, jars,clamps, tractors, stabilizers, fishing tools, or combinations thereof.

The present embodiments disclose the pistons forming at least oneextendable arm that is configured to extend away from the drill stringand come into contact with a formation. The pistons may be configured totranslate in a direction normal to a rotational axis of the housing andmay be configured to actuate independently or in combinations with eachother.

FIG. 11 discloses an embodiment of a drill string 1101 comprising atleast one piston 1103 disposed in at least one wall 1102. The wall 1102may have a greater diameter than a diameter of the drill string 1101.The piston 1103 may comprise a plurality of cutting elements 1104 andthe cutting elements 1104 may be configured to contact and degrade aformation. With the cutting elements 1104 configured to degrade theformation, the piston 1103 may form a reamer which when in an extendedposition may enlarge the diameter of a wellbore. There are manyinstances in drilling operations, such as a collapse of the wellbore,that it is desirable for the wellbore diameter to be enlarged. Thepiston 1103 may extend and the drill string 1101 may rotate causing thecutting elements 1104 to degrade the formation.

Valleys 1105 may be formed between walls. The valleys 1105 may allowdrilling mud and debris to travel between the drill string 1101 and theformation during normal drilling operations. The wall 1102 may beconfigured to partially curve or spiral around the drill string 1101.The valleys 1105 may thus also curve or spiral around the drill string1101 which may force the drilling mud and debris to spiral around thedrill string 1101 as it travels up the annulus of the wellbore. Byspiraling, the drilling mud may exert forces on the drill string 1101which may help the drill string 1101 rotate.

FIG. 12 discloses an embodiment of a drill string 1201 comprising atleast one piston 1203 disposed in at least one wall 1202. Each piston1203 may comprise a plurality of cutting elements 1204 and the cuttingelements 1204 may be configured to grip a formation. As shown in theembodiment, the cutting elements 1204 may comprise a conical shape thatis used to penetrate and clamp onto the formation. By clamping onto theformation, a portion of the drill string 1201 below the piston 1203 maybecome isolated from a portion of the drill string 1201 above the piston1203. The isolated portion of the drill string 1201 may not be subjectto the rotational forces applied to the top portion of the drill string1201 by a top drive disposed at the surface and thus be able to rotateas desired from motors or other power devices disposed in the isolatedportion.

The piston 1203 may also be configured to clamp onto the formation withmaximum efficiency due to the ability of the piston 1203 to actuateindependently of other pistons. The formation may not comprise an evensurface for the piston 1203 to clamp on to so actuating independentlymay allow the piston 1203 to clamp onto as much of the formation aspossible.

Incorporated into the piston 1203 may be a formation hardness testingmechanism. It is believed that the type of formation may be determinedby measuring its hardness. The piston 1203 may extend and the cuttingelements 1204 may contact the formation. The forces applied to thepiston 1203 and the amount the cutting elements 1204 penetrate into theformation may be used to determine the hardness of the formation.

The piston 1203 may be configured to work in combination with each othersuch that the piston 1203 may push on one side of the formation forcingthe drill string 1201 against the opposite side. Forcing the drillstring 1201 against one side of the formation may be desirable whenmeasurements, such as resistivity or seismic, are taken. With the drillstring 1201 in contact with the formation, the measurements may be ableto better identify signals as they propagate through the formation.

FIG. 13 discloses a drill string 1301 comprising walls in a plurality ofdifferent locations along the drill string 1301. In this embodiment, twolocations on the drill string 1301 each comprise at least one wall. Atop location 1302 may be disposed closer to the surface, and a bottomlocation 1303 may be disposed closer to the drill bit. Each location maycomprise walls 1304 and 1305 respectively with a plurality of pistons1306 and 1307 disposed thereon. The pistons 1306 and 1307 at eachlocation may comprise cutting elements that may be configured to gripinto a formation. The plurality of locations 1302 and 1303 may operatemutually to form a crawler or tractor tool. A portion of the drillstring 1308 may be disposed between the top and bottom locations 1302and 1303 and may comprise telescoping capabilities. The crawler ortractor tool may function by the pistons 1306 in the top location 1302extending and clamping onto the formation. Motors and other powerdevices may move the bottom location 1303 further into the wellbore andthe telescoping portion of the drill string 1308 may elongate. After thebottom location 1303 has moved a desired amount, the pistons 1307 in thebottom location 1303 may extend and clamp onto the formation. Thepistons 1306 in the top location 1302 may then retract and thetelescoping portion of the drill string 1308 may contract. Through thesemovements, the drill string 1301 may move to a desired position withinthe wellbore.

In some embodiments, sensors, such as resistivity or seismic sensors mayalso be disposed within the telescoping portion of the drill string. Thepistons at each location may extend and clamp onto the formation. Thesensors disposed between the top location and the bottom location mayidentify signals traveling through the formation because of the contactof the top and bottom locations with the formation. The signals maypropagate through the formation and pistons to the sensors.

FIG. 14 discloses an embodiment of a drill string 1401 comprising atleast one piston 1403 disposed in at least one wall 1402. The piston1403 may comprise at least one sensor 1404. The at least one sensor maycome from a group consisting of pressure transducers, lineardisplacement variable transformers (LDVTs), resistivity sensors, seismicsensors, or combinations thereof. The piston 1403 may extend and contactthe formation allowing the sensor 1404 to gather information from theformation.

In some embodiments, the piston 1403 may comprise calipers that may beconfigured to measure the distance that the piston 1403 extended beforecontacting the formation. Because the piston 1403 may act independentlyof other pistons, the diameter of the wellbore at the locations of thepiston 1403 may be accurately measured.

FIG. 15 discloses a cross-sectional view of an embodiment of a drill bit1501 comprising a cutting lace 1502. The drill bit 1501 may alsocomprise a bore 1503 through which drilling fluid may travel. At leastone chamber 1504 may be formed on the bore 1503 such that it opens tothe cutting face 1502. A piston 1505 may be disposed within the chamber1504 and be configured to translate in a direction parallel to arotational axis 1506 of the drill bit 1501. The piston 1505 may comprisean indenting element 1507 configured to contact the formation as thepiston 1505 extends and retracts.

Whereas the present invention has been described in particular relationto the drawings attached hereto, it should be understood that other andfurther modifications apart from those shown or suggested herein, may bemade within the scope and spirit of the present invention.

What is claimed is:
 1. A piston assembly, comprising: a housingcomprising a wall; at least one chamber formed in the wall; a pistondisposed within the chamber; wherein the piston comprises a workingsurface adjacent the wall, a base surface opposite the working surface,and an intermediate surface joining the working surface and the basesurface; at least one passageway through the piston; wherein the basesurface comprises an opening to the passageway; at least one pindisposed within the passageway and attached to the chamber; and whereinthe piston is free to translate relative to the pin.
 2. The assembly ofclaim 1, wherein the chamber is in fluid communication with a fluidsource.
 3. The assembly of claim 1, wherein the housing is selected froma group consisting of drill bits, calipers, reamers, shock absorbers,jars, clamps, tractors, stabilizers, fishing tools, and combinationsthereof.
 4. The assembly of claim 3, wherein the housing consists of adrill bit and the wall and the chamber are disposed on a gauge surfaceof the drill bit.
 5. The assembly of claim 1, wherein the housingcomprises a tube and the wall is disposed within the tube.
 6. Theassembly of claim 1, wherein the housing comprises a tube and the wallis disposed on a surface of the tube.
 7. The assembly of claim 1,wherein the chamber comprises a cross section selected from the groupconsisting of a circle, oval, polygon, star, rectangle with circularends, and annulus.
 8. The assembly of claim 1, wherein the pistoncomprises a cross sectional shape similar to the chamber.
 9. Theassembly of claim 1, wherein the chamber comprises openings to allowpassage of the pin and fluid communication with the chamber.
 10. Theassembly of claim 1, wherein the chamber is lined with a sleeve and thesleeve comprises openings to allow passage of the at least one pin. 11.The assembly of claim 1, wherein the passageway intersects at least oneof the intermediate surface and base surface.
 12. The assembly of claimwherein the working surface comprises wear resistant elements disposedthereon.
 13. The assembly of claim 1, wherein the base surface isnonplaner and comprises a topography selected from the group consistingof grooves, dimples, flutes, fins, troughs, and protrusions.
 14. Theassembly of claim 1, wherein the pin comprises a cross section selectedfrom the group consisting of a circle, oval, polygon, star, rectanglewith circular ends, and annulus.
 15. The assembly of claim 1, whereinthe pin comprises an aperture there through.
 16. The assembly of claim1, wherein the pin comprises a sleeve surrounding at least a portion ofthe pin.
 17. The assembly of claim 1, wherein the passageway comprises across-sectional area greater than a cross-sectional area of the pin. 18.The assembly of claim 1, further comprising a seal disposed between thechamber and the piston, the piston and the sleeve, or the chamber andthe sleeve.
 19. A piston assembly, comprising: a housing comprising awall, the housing having a longitudinal axis; a first piston disposedwithin the wall and configured to translate relative to the housing; anda second piston disposed within the wall and configured to translaterelative to the housing, the second piston being offset from the firstpiston in a direction along the longitudinal axis, and at least a partof the second piston overlapping at least a part of the first pistonabout the longitudinal axis, wherein the first piston and the secondpiston are configured to actuate independently.
 20. The piston assemblyof claim 19, wherein the first piston is retained within the wall of thehousing by contact with a shoulder.
 21. The piston assembly of claim 19,further comprising a first chamber and a fluid channel in communicationwith at least the first chamber, the first piston positioned at leastpartially within the first chamber.
 22. The piston assembly of claim 19,wherein the second piston is angularly aligned with the first pistonrelative to the longitudinal axis.
 23. The piston assembly of claim 19,wherein the first piston and second piston are configured to translaterelative to the housing at a specific time period.
 24. The pistonassembly of claim 19, further comprising a pin extending through thefirst piston and part of the housing, the pin configured to limitrotational and translational movement of the first piston relative tothe housing.
 25. The piston assembly of claim 19, wherein at least partof the first piston or second piston includes diamond.
 26. The pistonassembly of claim 25, further comprising at least one cutting elementpositioned on a working surface of the first piston or the secondpiston.
 27. The piston assembly of claim 19, further comprising a sealpositioned between the first piston and the wall of the housing.
 28. Thepiston assembly of claim 19, wherein the housing is selected from agroup consisting of drill bits, calipers, reamers, shock absorbers,jars, clamps, tractors, stabilizers, fishing tools, and combinationsthereof.
 29. The piston assembly of claim 19, wherein the first pistonand the second piston are configured to actuate independently and incombination with each other.
 30. A method of steering a drilling system,the method comprising: positioning a piston assembly adjacent aformation, the piston assembly including a first piston and a secondpiston, the second piston being offset from the first piston along alongitudinal axis of the piston assembly; opening a valve to redirect aportion of drilling fluid; extending the first piston radially using theportion of the drilling fluid applied to a base surface of the firstpiston; contacting the formation with the first piston; extending thesecond piston radially using the portion of the drilling fluid appliedto a base surface of the second piston; and contacting the formationwith the second piston, wherein contacting the formation with the firstpiston and the second piston pushes the drilling system to move in adesired direction.
 31. The method of claim 30, wherein extending thefirst piston and extending the second piston occur at different times.32. The method of claim 30, wherein extending the first piston includesapplying a fluid pressure to the base surface of the first piston. 33.The method of claim 30, wherein the first piston and the second pistonare both extended by a fluid pressure of a single fluid source.
 34. Themethod of claim 30, further comprising: measuring a first distancetraveled by the first piston while extending the first piston, whereinmeasuring the first distance includes measuring with a first set ofcalipers connected to the first piston; and measuring a second distancetraveled by the second piston while extending the second piston, whereinmeasuring the second distance includes measuring with a second set ofcalipers connected to the second piston.
 35. The method of claim 30,wherein extending the first piston and extending the second piston occurat different times.
 36. The method of claim 30, wherein the portion ofthe drilling fluid is applied to the base surface of the first pistonand the portion of the drilling fluid is applied to the base surface ofthe second piston by activating the valve.
 37. The method of claim 30,further comprising connecting a bit to the piston assembly.
 38. Adownhole tool comprising: a body comprising a wall, the body having alongitudinal axis and an outer surface; a first chamber in the wall andhaving an opening in the outer surface of the body; a first pistonpositioned in the first chamber and configured to translate within thefirst chamber and relative to the body; a second chamber in the wall andhaving an opening in the outer surface of the body; a second pistonpositioned in the second chamber and configured to translate relative tothe body, the second piston being axially displaced from the firstpiston along the longitudinal axis, and at least a part of the secondpiston angularly overlapping at least a part of the first piston aboutthe longitudinal axis; and a valve configured to redirect a portion of adrilling fluid to contact the first piston and the second piston tocause the first piston and the second piston to actuate.
 39. The tool ofclaim 38, wherein the first piston includes at least one sensor.
 40. Thetool of claim 39, wherein the at least one sensor includes at least oneof a pressure transducer, linear displacement variable transformer,resistivity sensor, or seismic sensor.
 41. The piston assembly of claim38, further comprising a cutting structure.
 42. The piston assembly ofclaim 41, wherein the cutting structure includes a bit.
 43. The pistonassembly of claim 42, wherein the wall is on a gauge surface of the bit.44. The piston assembly of claim 41, wherein the cutting structureincludes at least one of a bit, a caliper, a reamer, a shock absorber, ajar, a clamp, a tractor, a stabilizer, or a fishing tool.